DNAv4
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... IPv4 Link-Local
addresses [RFC3927], a set of steps known as Detecting Network
Attachment for IPv4 (DNAv4). DNAv4 optimizes the (common) case of
re-attachment to a network ...
... RFC3927], a set of steps known as Detecting Network
Attachment for IPv4 (DNAv4). DNAv4 optimizes the (common) case of
re-attachment to a network that one has been connected to previously
...
... address previously
obtained on the new network is still operable, DNAv4 enables the host
to confirm the new configuration quickly, bypassing restart ...
... disappear into the void without doing any damage.
These issues that define the applicability of DNAv4 lead us to a
number of conclusions:
...
... number of conclusions:
o DNAv4 is a performance optimization. Its purpose is to speed
up a process that may require as much as a few hundred
...
... performance optimization, it must not sacrifice
correctness. In other words, false positives are not
acceptable. DNAv4 must not conclude that a host has returned
to a previously visited link ...
... unicast ARP Requests,
then DNAv4 will not be able to detect that it has returned to
the same link in the future. This is acceptable because the
...
... same link in the future. This is acceptable because the
host still operates correctly as it did without DNAv4, just
without the performance benefit. Users and network operators ...
... network operators
who desire the performance improvement offered by DNAv4 can
upgrade their routers to support DNAv4 ...
...
o As a performance optimization, where DNAv4 fails to provide a
benefit, it should add little or no delay compared to today's
DHCP ...
... DHCP processing. In practice, this implies that DHCP
processing needs to proceed in parallel. Waiting for DNAv4 to
fail before beginning DHCP processing can greatly increase
...
... total processing time, the opposite of the desired effect.
o Trials are inexpensive. DNAv4 performs its checks using small
unicast packets. An IPv4 ...
... found to be the correct one.
o Time is limited. If DNAv4 is to be effective in enabling low
latency handoffs, it needs to complete in less than 10 ms.
...
... interface's no longer being capable of
communicating data frames; transient periods of high frame loss
are not sufficient. DNAv4 does not utilize "Link Down"
indications.
...
... reachability test. Other routes SHOULD be re-learned.
DNAv4 does not significantly increase the likelihood of an address
conflict. The reachability ...
... Section 2.1.1.
One case where DNAv4 does increase the likelihood of an address
conflict is when:
...
... this risk, though this also limits the operable candidate
configurations available for DNAv4 to try.
...
... reachability tests, with the host using the first answer returned.
This ensures that the DNAv4 procedure will not result in additional
delay in the case where reachability tests fail, or where sending a
...
... tests that do not elicit a response.
Where DNAv4 and DHCP are tried in parallel, one strategy is to
forsake reachability ...
... reachability test retransmissions and to allow only the DHCP
client to retransmit. In order to reduce competition between DNAv4
and DHCP retransmissions ...
... and DHCP retransmissions, a DNAv4 implementation that retransmits may
utilize the retransmission strategy described in Section 4.1 of the
...
... DHCP message,
pending retransmissions are canceled. It is RECOMMENDED that a DNAv4
implementation retransmit no more than twice. To provide damping in
the case of spurious "Link ...
... the case of spurious "Link Up" indications, it is RECOMMENDED that
the DNAv4 procedure be carried out no more than once a second.
...
... IPv4 Link-Local Addresses" [RFC3927] and
MUST NOT attempt to use DNAv4 as a shortcut to bypass that process.
...
...
An implementation may use DNAv4 to confirm the configuration of
manually assigned addresses. However, special consideration is
...
... enabled by default.
For the purposes of DNAv4, manually assigned addresses may be treated
as equivalent to DHCP ...
... address. In this case, a host utilizing
DNAv4 could confirm an address that had been assigned to another
host ...
... dynamically assigned address was not suitable for some reason.
Therefore, where DNAv4 and DHCP are run in parallel and DNAv4
...
... Therefore, where DNAv4 and DHCP are run in parallel and DNAv4
confirms a manual configuration, it may be undesirable to allow this
...
... home network could be compromised
by spoofing of the DNAv4 reachability test. In general, adjustment
of the security ...
... reachability test. In general, adjustment
of the security configuration based on DNAv4 is NOT RECOMMENDED.
Hosts ...
... Hosts that depend on secure IP configuration SHOULD NOT use DNAv4 but
SHOULD instead utilize DHCP authentication [RFC3118 ...